ABSTRACT
BACKGROUND: Cobalamin C (CblC) defects are inherited autosomal recessive disorders of vitamin B12 metabolism due to mutations in the MMACHC gene. Renal manifestations include thrombotic microangiopathy (TMA), acute or chronic renal failure, tubulointerstitial nephritis, and proximal renal tubular acidosis. However, reports about glomerular pathologies are scarce. CASE REPORT: A 4-year-old boy presented with nephrotic syndrome, arterial hypertension, and chronic anemia but no signs of hemolysis. Renal biopsy showed TMA with ischemic glomerular collapse, foot process effacement, and tubulointerstitial fibrosis. Elevated serum levels of homocysteine suggested a cobalamin C disorder. This was confirmed by the identification of compound heterozygous mutations in the MMACHC gene. Initial therapy consisted of antihypertensive treatment including angiotensin converting enzyme inhibitor (ACEi) leading to blood pressure control and a significant reduction of proteinuria. After a definite diagnosis of CblC deficiency, hydroxocobalamin was introduced. Thereafter, homocysteine levels decreased, anemia resolved, and a further decline of proteinuria with normalization of serum protein levels was noted. Renal function remained stable. CONCLUSIONS: Although uncommon, the clinical picture of CblC defects may be ruled by nephrotic syndrome mimicking glomerulonephritis, minimal change disease, or primary focal and segmental glomerulosclerosis. Key to a correct diagnosis is elevated serum levels of homocysteine, and a definite diagnosis can be confirmed by genetic testing.
Subject(s)
Nephrotic Syndrome/etiology , Thrombotic Microangiopathies/etiology , Vitamin B 12 Deficiency/complications , Vitamin B 12/metabolism , Anemia/etiology , Angiotensin-Converting Enzyme Inhibitors/therapeutic use , Biopsy , Carrier Proteins/genetics , Child, Preschool , Homocysteine/blood , Humans , Hydroxocobalamin/therapeutic use , Hypertension, Renal/drug therapy , Hypertension, Renal/etiology , Hypertension, Renal/pathology , Kidney/pathology , Male , Nephrotic Syndrome/drug therapy , Nephrotic Syndrome/pathology , Oxidoreductases , Thrombotic Microangiopathies/drug therapy , Thrombotic Microangiopathies/pathology , Vitamin B 12 Deficiency/genetics , Vitamin B 12 Deficiency/pathologyABSTRACT
BACKGROUND: In May and June 2011 the largest known outbreak of hemolytic uremic syndrome (HUS) occurred in northern Germany. Because, quite unusually, a large number of adults was affected and the causative Escherichia coli strain, serotype O104:H4, showed an atypical virulence factor pattern, it was speculated that this outbreak was associated with an aggressive course and an unfavorable prognosis also in children. METHODS: Retrospective analysis of medical records of 90 children and comparison to previous outbreak and sporadic case series. RESULTS: Median age was unusually high (11.5 years) compared with that in historical series. Only 1 patient (1.1%) died in the acute phase. Most patients (67/90 [74%]) received supportive care only. Renal replacement therapy was required in 64 of 90 (71%) of the children. Neurological complications, mainly seizures and altered mental stage, were present in 23 of 90 (26%) patients. Ten patients received plasmapheresis, 6 eculizumab, and 7 a combination of both. After a median follow-up of 4 months, renal function normalized in 85 of 90 (94%) patients, whereas 3 patients had chronic kidney disease stage 3 or 4, and 1 patient (1.1%) still requires dialysis. Complete neurological recovery occurred in 18 of 23 patients. Mild to moderate and major residual neurological changes were present in 3 patients and 1 patient, respectively, although all patients were still improving. CONCLUSIONS: E. coli O104:H4 caused the largest HUS outbreak in children reported in detail to date and most patients received supportive treatment only. Initial morbidity, as well as short-term outcome, due to this pathogen, is comparable to previous pediatric series of Shiga toxin-producing E. coli HUS.
